The chain checker tool offers arguably the greatest potential to save money of any workshop tool. The cost of replacing drivetrain components prematurely aged by a worn chain can run into hundreds of pounds. Even the most sophisticated chain checker tool is unlikely to cost more than about £25.
A cassette can outlast up to four chains, if the chains are replaced before the become excessively worn, Jon says. It’s hard to overstate the force to which a chain is subjected. Pedaling places it under tension, and the tension causes it to stretch. Over time, the shape of the teeth on the cassette and chainrings will mirror that of the worn chain links.
Ride use a Park Tool that locates in the chain with two pins, pictured above. The distance travelled by the measurement dial in its arc indicates the wear suffered by the chain. Other chain checker tools are available; Park, for example, make a cheaper unit with two fixed pins. When the length of a stretched link exceeds the distance between the two pins, it’s time for a new chain.